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Lysine for Feline Upper Respiratory Tract Disease

Drazenovich, T. L., A. J. Fascetti, et al. (2009). “Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter.” Am J Vet Res 70(11): 1391-400.

Feline herpesvirus (FHV) is a common cause of respiratory infections in cats housed in shelter situations. Cats latently infected with feline herpesvirus are important sources of the virus for cats that are susceptible to infection. Medications that interfere with latency establishment or reactivation of latent infections would be extremely useful, especially in rescue facilities, where animals are often highly stressed, and have variable vaccination history and immune status. Lysine has shown promise in mediating antiviral effects in cats. These researchers investigated the usefulness of dietary supplementation with lysine for cats in shelters to decrease incidence of infection and detection of FHV shedding. Using 261 adult cats, basal diets (control group) and diets supplemented with lysine (treated group) were fed for four weeks. Unexpectedly, they found that treated cats were actually more likely to manifest severe disease than untreated controls at certain time points in the study (week 4). In addition, FHV was detected more commonly in treated cats (found in week 2 only). A confounding factor was that cats in both groups were also allowed access to commercial diets when hospitalized for illness in addition to the control and test diets. The researchers concluded that continuous dietary supplementation with lysine did not successfully control respiratory disease in a shelter situation, and is not an optimal use of funds in rescue facilities. Bolus treatment of cats with lysine may provide better plasma lysine levels than continuous dietary supplementation, and may provide more beneficial effects.
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Related articles:
Maggs, D. J., J. E. Sykes, et al. (2007). “Effects of dietary lysine supplementation in cats with enzootic upper respiratory disease.” J Feline Med Surg 9(2): 97-108.
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Rees, T. M. and J. L. Lubinski (2008). “Oral supplementation with L-lysine did not prevent upper respiratory infection in a shelter population of cats.” J Feline Med Surg 10(5): 510-3.
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